Abstract. Increases in surface ozone (O3) and fine particulate
matter (≤2.5 μm aerodynamic diameter, PM2.5) are associated
with excess premature human mortalities. We estimate changes in surface
O3 and PM2.5 from pre-industrial (1860) to present (2000) and the
global present-day (2000) premature human mortalities associated
with these changes. We extend previous work to differentiate the
contribution of changes in three factors: emissions of short-lived air
pollutants, climate change, and increased methane (CH4) concentrations,
to air pollution levels and associated premature mortalities. We use a
coupled chemistry-climate model in conjunction with global population
distributions in 2000 to estimate exposure attributable to concentration
changes since 1860 from each factor. Attributable mortalities are estimated
using health impact functions of long-term relative risk estimates for
O3 and PM2.5 from the epidemiology literature. We find global mean
surface PM2.5 and health-relevant O3 (defined as the maximum
6-month mean of 1-h daily maximum O3 in a year) have increased by
8 ± 0.16 μg m−3 and 30 ± 0.16 ppbv (results reported as
annual average ±standard deviation of 10-yr model simulations),
respectively, over this industrial period as a result of combined changes in
emissions of air pollutants (EMIS), climate (CLIM) and CH4
concentrations (TCH4). EMIS, CLIM and TCH4 cause global
population-weighted average PM2.5 (O3) to change by
+7.5 ± 0.19 μg m−3 (+25 ± 0.30 ppbv),
+0.4 ± 0.17 μg m−3 (+0.5 ± 0.28 ppbv), and
0.04 ± 0.24 μg m−3 (+4.3 ± 0.33 ppbv), respectively. Total global changes in
PM2.5 are associated with 1.5 (95% confidence interval, CI, 1.2–1.8)
million cardiopulmonary mortalities and 95 (95% CI, 44–144) thousand lung
cancer mortalities annually and changes in O3 are associated with 375
(95% CI, 129–592) thousand respiratory mortalities annually. Most air
pollution mortality is driven by changes in emissions of short-lived air
pollutants and their precursors (95% and 85% of mortalities from
PM2.5 and O3 respectively). However, changing climate and
increasing CH4 concentrations also contribute to premature mortality
associated with air pollution globally (by up to 5% and 15%,
respectively). In some regions, the contribution of climate change and
increased CH4 together are responsible for more than 20% of the
respiratory mortality associated with O3 exposure. We find the
interaction between climate change and atmospheric chemistry has influenced
atmospheric composition and human mortality associated with industrial air
pollution. Our study highlights the benefits to air quality and human health
of CH4 mitigation as a component of future air pollution control
policy.